On 01/19/2016 10:55 AM, Heiko Carstens wrote: > On Mon, Jan 18, 2016 at 07:48:16PM +0100, Christian Borntraeger wrote: >> On 01/18/2016 07:32 PM, Peter Zijlstra wrote: >>> On Fri, Jan 15, 2016 at 04:13:34PM +0100, Christian Borntraeger wrote: >>>>> Yes, the deadlock is gone and the system is still running. >>>>> After some time I had the following WARN in the logs, though. >>>>> Not sure yet if that is related. >>>>> >>>>> [25331.763607] DEBUG_LOCKS_WARN_ON(lock->owner != current) >>>>> [25331.763630] ------------[ cut here ]------------ >>>>> [25331.763634] WARNING: at kernel/locking/mutex-debug.c:80 >>> >>>> I restarted the test with panic_on_warn. Hopefully I can get a dump to check >>>> which mutex this was. >>> >>> Hard to reproduce warnings like this tend to point towards memory >>> corruption. Someone stepped on the mutex value and tickles the sanity >>> check. >>> >>> With lockdep and debugging enabled the mutex gets quite a bit bigger, so >>> it gets more likely to be hit by 'random' corruption. >>> >>> The locking in seq_read() seems rather straight forward. >> >> I was able to reproduce. The dump shows a mutex that has an owner field, which >> does not exists as a task so this all looks fishy. The good thing is, that I >> can reproduce the issue within some hours. (exact same backtrace). Will add some >> more debug data to get a handle where we come from. > > Did the owner field show to something that still looks like a task_struct? No, its not a task_struct. Activating some more debug information did indeed revealed several other issues (overwritten redzones etc). Unfortunately I only saw the broken things after the facts, so I do not know which code did that. When I disabled the cgroup controllers in libvirt I was no longer able to trigger the bugs. Still trying to narrow things down. Christian -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
